I am asked by a client to cut out a profile in eps polystyrene. I don't know much about hotwire cutting, only experiments years ago with very fine wire. The best way to do this looks like attaching a profile of bent Nichrome wire to my cnc and running along the foamboard but the is conjecture on my part.

The outline of the profile i'm trying to cut out is roughly the shape of half a cog, i.e. semi circle and four teeth. The length of wire required to form the shape is about 20cm, or 8 inches in length.

From looking at examples of hand held hotwire cutters its looks like they use ribbon wire instead of round wire, i'm guessing as that profile is less likely to bend? I bought some round 19 gauge nichrome wire, which my 50v/5amp bench top supply can't heat hot enough.

My question is can anyone suggest a gauge of ribbon wire or even round wire I should be looking at to hold its profile where 8 inches of wire are required to pass through the foam in a single pass?

Any thoughts welcome